Yours', Mine's, Theirs', His'

[Sped Tiger]

I know that those are possessive pronouns on their own, but I also know that they can be used in different cases: dative, nominative accusative, and also genitive. My question has to do with whether we should use an apostrophe when using possessive pronouns in genitive or not.

Examples of them in accusative and dative and nominative: 1) My cat is a real jumper. Is yours too?; 2) My car is robust. Is hers robust too?; 3) I've fed my kitten. Have you fed yours?; 4) I gave my friend a present, and they gave one to theirs.

Examples in genitive (which is correct?): 1) My cats' behavior is stable. Is yours'/yours's/yours stable too? (= Is yours cats' behavior stable too?); 2) My wife's ring is made of silver, and what about John? Is his'/his's/his made of silver too? (= his wife's)
If we do have to genitivize possessive pronouns in this case, what is the pronunciation, then?

 

[Rover_KE]

All your examples of possessive pronouns with apostrophes are wrong.

 

[jutfrank]

We don't use apostrophes with possessive pronouns at all.

 

[Sped Tiger]

We don't use apostrophes with possessive pronouns at all.

So, is it correct to write "My cat's friend is fabulous. Is yours?" (yours')

 

[5jj]

So, is it correct to write "My cat's friend is fabulous. Is yours?" (yours')

Yes, if you mean 'Is your cat fabulous?'

 

[jutfrank]

So, is it correct to write "My cat's friend is fabulous. Is yours?" (yours')

Are you asking about my cat or my cat's friend?

The question is grammatical, but grammatically ambiguous. You could be asking about either.

 

[emsr2d2]

Cats don't, as a rule, have friends.

 

[Sped Tiger]

Are you asking about my cat or my cat's friend?

The question is grammatical, but grammatically ambiguous. You could be asking about either.

About your cat's friend.

 

[Rover_KE]

Cats don't, as a rule, have friends.

They have servants — us.